The hydrothermal system of Mendeleev Volcano, Kunashir Island, Kuril Islands: The geochemistry and the transport of magmatic components

摘要

This paper reports a detailed geochemical study of thermal occurrences as observed in the edifice and on the flanks of Mendeleev Volcano, Kunashir Island in August and September 2015. We showed that three main types of thermal water are discharged there (neutral chloride sodium, acid chloride sulfate, and acid sulfate types); these waters exhibit a zonality that is typical of volcano-hydrothermal island arc systems. Spontaneous and solfataric gases have relatively low He-3/He-4 ratios, ranging between 5.4Ra and 5.6Ra, and delta C-13-CO2 between -4.8aEuro degrees and -3.1aEuro degrees, and contain a light isotope of carbon in methane (delta C-13 ae -40aEuro degrees). Gas and isotope geothermometers yield relatively low temperatures around 200A degrees C. The isotope compositions in all types of water are similar to that of local meteoric water. The distribution of microcomponents varies among different types. The isotope composition of dissolved Sr varies considerably, from 0.7034 as observed in Kunashir rocks on an average to 0.7052 in coastal springs, which may have resulted from admixtures of seawater. The total hydrothermal transport rates of magmatic Cl and SO4, as observed for Mendeleev Volcano, are 7.8 t/d and 11.6 t/d, respectively. The natural outward transport of heat by the volcano's hydrothermal system is estimated as 21 MW.